Keeping Water Out with Rainscreens

Keeping water out of interiors of buildings is one of the architects’ main duties in any project and one of prominent causes of litigation. Waterproofing systems, therefore, are crucial to the success of a project for the architect, contractor, and owner, and architects and contractors probably spend more time ensuring a building is watertight by researching and detailing than any other component of a project. Researching and understanding new systems is essential in continuing to improve in this area.

There are a few ways to keep a building dry and mold-free: Make sure water stays out, get water out quickly if(when) it gets in, and dry out whatever becomes wet as quickly as possible. Water inevitably gets where it shouldn’t be. The challenge is often how to get it out when it gets in. Caulk is essential in keeping water out and flashing is indispensible for dealing with water infiltration, but good air flow is often overlooked as a means to keep cladding systems and therefore a building dry.

One innovative waterproofing system that addresses this is the Rainscreen System. This is a generic term for a cladding system where the cladding/siding is held off the exterior wall by some distance with furring strips, allowing air to circulate behind the siding freely and therefore dry out the assembly much more quickly. Rainscreen systems are unique from many other siding systems in that they allow water behind the siding much more easily, and rely on the building wrap to keep it out of the wall, but water isn’t allowed to sit stagnant for long periods of time because air flow dries out the cavity behind the siding.

This diagram is from our computer model of a project that is being constructed in Ankeny that we are using a rainscreen system on. In addition to its moisture benefits, rainscreen systems can create a wide variety of different looks. We used a fiber-cement panel with aluminum J-channel to create a modern look on this project, but more traditional aesthetics can easily be achieved as well. The cladding is installed over furring strips, creating the air gap between the wall and the cladding. We used a regular pattern of exposed fasteners to attach the panels, which creates an intentional feeling pattern with a modern-industrial feel. The look will work great for this project, but even more importantly, the wall will be allowed to dry out after getting moisture and perform well for decades to come, saving long term costs and maintenance work.